JP2008035620A - Bidirectional dc-dc converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To save space and reduce cost with respect to a bidirectional DC-DC converter for charging and discharging a battery. <P>SOLUTION: First to fourth field effect transistors Q1 to Q4 are connected in full bridge configuration. A power supply 3 is connected to one set of the opposite electrodes (between the point of junction between the first and third field effect transistors Q1, Q3, and the point of junction between the second and fourth field effect transistors Q2, Q4) of this full bridge connection. A battery 1 is connected to the other set of the opposite terminals (between the point of junction between the first and second field effect transistors Q1, Q2 and the point of junction between the third and fourth field effect transistors Q3, Q4) through a choke coil L1. A control unit 4 is provided which controls turn-on/off of the first to fourth field effect transistors Q1 to Q4 to charge or discharge the battery 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a bidirectional DC-DC converter that controls charging and discharging of a battery in a battery characteristic test or the like.

  The battery characteristic test measures charging characteristics based on charging current and terminal voltage, discharging characteristics based on discharging current and terminal voltage, and charging / discharging characteristics by repeated charging and discharging. Therefore, it is common to provide a charging device for charging the battery and a discharging device such as an electronic load device for discharging. For example, as shown in FIG. 11, a bias power source 101, a step-up chopper circuit 102, a step-down chopper circuit 103, and a power source 104 are provided for the battery 100 to be tested, and the voltage of the power source 104 is stepped down by the step-down chopper circuit 103. The battery 100 is charged and discharged by making the voltage higher than the voltage of the power supply 104 by the boost chopper circuit 102 via the bias power supply 101 for enabling discharge even when the terminal voltage of the battery 100 is about zero. The discharge is made to return.

However, providing dedicated devices such as the step-down chopper circuit 103 for charging the battery and the step-up chopper circuit 102 for discharging in this way is disadvantageous in terms of space and cost. In view of this, a bidirectional DC-DC converter in which a part of each configuration for charging and discharging is shared has been proposed (for example, see Patent Document 1). This bidirectional DC-DC converter is configured to perform either a step-down chopper circuit or a step-up chopper circuit, and performs a switching operation as a step-down chopper circuit when charging a battery. When a transistor is operated and a parasitic diode of a field effect transistor constituting a step-up chopper circuit is used, and a battery is discharged, a field effect transistor performing a switching operation is operated as a step-up chopper circuit and a step-down operation is performed. In this configuration, a parasitic diode of a field effect transistor that constitutes a type chopper circuit is used. A full bridge converter in which switching elements such as field effect transistors are bridge-connected is used in various power supply devices (see, for example, Patent Document 2).
JP 2003-304644 A JP 2006-67672 A

  For example, the configuration shown in FIG. 11 of the conventional example uses dedicated configurations for charging and discharging the battery, which is disadvantageous in terms of space and cost. The bidirectional DC-DC converter can share a part of the configuration of the step-down chopper circuit for charging and the step-up chopper circuit for discharging to improve the space and cost, but it is still There are problems that are not enough.

  An object of the present invention is to solve the conventional problems, and to share a configuration for charging and discharging a battery to reduce space and cost.

  A bidirectional DC-DC converter according to the present invention is a bidirectional DC-DC converter that charges and discharges a battery. A field effect transistor is connected in a full bridge, and a power source is connected to one opposing terminal of the full bridge connection. Is connected to the other opposing terminal via a choke coil, and the field effect transistor is controlled to be turned on and off to charge or discharge the battery.

  In the bidirectional DC-DC converter for charging and discharging the battery, the first and second field effect transistors are connected in series, and the third and fourth field effect transistors are connected in series. A connection point between the first field effect transistor and the third field effect transistor and a connection point between the second field effect transistor and the fourth field effect transistor are connected to a power source, and the first electric field The battery is connected via a choke coil to a connection point between the effect transistor and the second field effect transistor and a connection point between the third field effect transistor and the fourth field effect transistor, To a control section for controlling on / off of the fourth field effect transistor to charge or discharge the battery.

  The control unit turns on the first and fourth field effect transistors and charges the battery from the power source via the choke coil, and then turns off the first and fourth field effect transistors. In this configuration, the battery charging current based on the energy stored in the choke coil is controlled to flow as regenerative power to the power source via the parasitic diodes of the second and third field effect transistors.

  The control unit turns on the first and fourth field effect transistors to charge the battery from the power source via the choke coil, and then turns on the fourth field effect transistor to turn on the fourth field effect transistor. In this configuration, the charging current of the battery is supplied by the energy stored in the choke coil via the field effect transistor and the parasitic diode of the second field effect transistor.

  The control unit turns on the second and third field effect transistors and discharges the battery via the choke coil with a voltage obtained by adding the voltage of the power source to the voltage of the battery, and the second and third field effect transistors are discharged. The third field effect transistor is turned off, and the sum of the voltage generated by the energy stored in the choke coil and the voltage of the battery is used as regenerative power to the power supply via the parasitic diodes of the first and fourth field effect transistors. It has the structure which performs control which continues discharge of a battery.

  The control unit turns on the second field effect transistor to discharge the battery via the second field effect transistor and a parasitic diode of the fourth field effect transistor, and thereby performs the second electric field effect. The effect transistor is turned off, and the battery is discharged as regenerative power to the power supply via the parasitic diodes of the first and fourth field effect transistors by the sum of the voltage of the energy stored in the choke coil and the voltage of the battery. It has the structure which performs control to continue.

  Since a configuration including a field effect transistor with a full bridge connection can be shared for battery charging and discharging, space saving and cost reduction can be achieved. Further, by using the energy stored in the choke coil, it is possible to eliminate the need for a bias power source when the battery is discharged.

  The bidirectional DC-DC converter of the present invention will be described with reference to FIG. 1. The first to fourth field effect transistors Q1 to Q4 are connected in a full bridge, and one opposing terminal (first , Third field effect transistors Q1 and Q3 and a connection point between second and fourth field effect transistors Q2 and Q4), and power supply 3 is connected to the other opposing terminal (first and first field effect transistors). The battery 1 is connected via a choke coil L1 between the connection point of the second field effect transistors Q1 and Q2 and the connection point of the third and fourth field effect transistors Q3 and Q4). The control unit 4 is configured to control on / off of the field effect transistors Q1 to Q4 to charge or discharge the battery 1.

  FIG. 1 is an explanatory diagram of a first embodiment of the present invention, in which 1 is a battery, 2 is a current detection unit, 3 is a power source, Vin + and Vin− are power supply voltages, 4 is a control unit, and 5 and 6 are operational amplifiers. An error amplifier 7, 7 is a control signal output unit, cont is a control signal instructing charging or discharging of the battery 1, as indicated by (charging / discharging), L 1 is a choke coil, C 1 and C 2 are capacitors, Q 1 to Q 4 are The diodes indicated by the dotted lines indicate the first to fourth field effect transistors and indicate parasitic diodes. Of the first to fourth field effect transistors Q1 to Q4, the first and second field effect transistors Q1 and Q2 are connected in series, and the third and fourth field effect transistors Q3 and Q4 are connected in series. A full bridge connection configuration, one opposing terminal of the full bridge connection, that is, a connection point between the first and third field effect transistors Q1 and Q3 and a connection point between the second and fourth field effect transistors Q2 and Q4. Is connected between the power supply 3 and the other opposing terminal, that is, between the connection point of the first and second field effect transistors Q1 and Q2 and the connection point of the third and fourth field effect transistors Q3 and Q4. Is connected to the battery 1 via the choke coil L1.

  Further, the charging current or discharging current of the battery 1 is detected by the current detection unit 2, and compared with the reference voltage ref by the error amplifier 5, and the difference is input to the error amplifier 6, and the pulse width is obtained by comparison with the sawtooth wave signal. A modulation signal is formed and input to the control signal output unit 7. The reference voltage ref is a value corresponding to a set value of a desired charging current or discharging current. The control signal output unit 7 controls on and off of the first to fourth field effect transistors Q1 to Q4 according to the control signal cont instructing charging or discharging of the battery 1, and controls the on period thereof.

  The battery charging and discharging operations will be described below with reference to FIGS. The current detection unit 2 and the control unit 4 are not shown. 2 to 5 show the operation when the battery is charged, and FIGS. 6 to 9 show the operation when the battery is discharged. The control stage is the first stage and the second stage Stage1 and Stage2, and each stage has In the field effect transistors Q1 to Q4, ON is indicated as ON, and OFF is indicated as no mark. Further, the ON period of the field effect transistor in each stage is controlled by the control unit 4 as described above so that the current value detected by the current detection unit 2 shown in FIG. 1 does not exceed the set value. Although the control stage is composed of the first and second stages, the control stage can be further increased to perform fine control.

  In the case of charging the battery, a control signal cont indicating charge control is input to the control signal output unit 7 of the control unit 4 shown in FIG. Thereby, a control signal for controlling on / off of the field effect transistors Q1 to Q4 is applied to each gate. In this charging control, either the control shown in FIGS. 2 and 3 or the control shown in FIGS. 4 and 5 can be selected. In FIG. By applying a control signal from the control signal output unit 7 (see FIG. 1) to the gate terminals indicated by black circles of the first and fourth field effect transistors Q1 and Q4, the field effect transistors Q1 and Q4 are turned on. 2. The third field effect transistors Q2 and Q3 are kept off. Thereby, a current flows from the power source 3 in the direction of the arrow to charge the battery 1. In the next second stage, as shown in FIG. 3, the first to fourth field effect transistors Q1 to Q4 are turned off. At this time, the energy stored in the choke coil L1 causes a current to flow in the direction of the arrow through the parasitic diodes of the second and third field effect transistors Q2 and Q3, and the battery 1 continues to be charged. Current flows in the direction of supply.

  The control shown in FIG. 4 and FIG. 5 is turned on by applying a control signal to the gate terminals indicated by black circles of the first and fourth field effect transistors Q1 and Q4 in the first stage. Field effect transistors Q2 and Q3 are turned off. Thereby, as shown in FIG. 4, the electric current of the arrow direction which charges the battery 1 flows. This first stage is the same as that shown in FIG. In the next second stage, as shown in FIG. 5, a control signal is applied to the gate terminal indicated by the black circle of the fourth field effect transistor Q4 to turn it on, and the first to third field effect transistors Q1 to Q3 are turned on. Turn off. As a result, the current stored in the arrow direction flows through the field effect transistor Q4 that is turned on and the parasitic diode of the field effect transistor Q2 that is turned off by the energy stored in the choke coil L1, thereby charging the battery 1. Continue.

  In the case of battery discharge, either the control shown in FIGS. 6 and 7 or the control shown in FIGS. 8 and 9 can be selected. In FIG. In one stage, a control signal is applied to the gate terminals indicated by black circles of the second and third field effect transistors Q2 and Q3 to turn them on. As a result, the discharge current of the battery 1 flows in the direction of the arrow due to the voltage resulting from the sum of the voltage of the battery 1 and the voltage of the power source 3. In this case, even when the voltage of the battery 1 is close to zero, the battery 1 can be discharged without requiring a bias power source. In the next second stage, as shown in FIG. 7, the first to fourth field effect transistors Q1 to Q4 are turned off. At this time, the voltage of the battery 1 is boosted by the energy stored in the choke coil L1, and the discharge current of the battery 1 flows to the power source 3 side through the parasitic diodes of the field effect transistors Q1 and Q4 as shown by the arrows. . Also in this discharge control, the ON period can be controlled so that the current detected by the current detector 2 shown in FIG. 1 does not exceed the set value.

  The control shown in FIGS. 8 and 9 is performed when the control signal is applied to the gate terminal indicated by the black circle of the second field effect transistor Q2 in the first stage and turned on as shown in FIG. The discharge current of the battery 1 flows in the direction of the arrow through the second field effect transistor Q2 and the parasitic diode of the fourth field effect transistor Q4 in the off state. In the next second stage, as shown in FIG. 9, the first to fourth field effect transistors Q1 to Q4 are turned off. At that time, the voltage of the battery 1 is boosted by the energy stored in the choke coil L1, and as indicated by an arrow on the power source 3 side through the parasitic diodes of the first and fourth field effect transistors Q1 and Q4, The discharging current of the battery 1 flows, and the discharging of the battery 1 can be continued.

  FIG. 10 is an explanatory diagram of Embodiment 2 of the present invention, in which 20 is a battery, 21 is a regenerative battery charge / discharge system, 22 is a bidirectional DC-DC converter, 23 is an AC regenerative converter, 24 is an insulation transformer, 25 Denotes a control computer, 26 denotes a safety protection unit, and 27 denotes a measurement unit. The bidirectional DC-DC converter 22 is the bidirectional DC-DC converter described in the first embodiment, and controls charging and discharging of the battery 20. Further, as a power source for the bidirectional DC-DC converter 22, a case where, for example, a three-phase AC 200V or 400V (3φ AC 200V / 400V) is used via an AC regenerative converter 23 and an insulating transformer 24 will be described.

  The control computer 25 controls the charging or discharging of the battery 20 by the bidirectional DC-DC converter 22, causes the measurement unit 27 to measure the charge / discharge characteristics of the battery 20, and controls the safety protection unit 26. The battery 20, the bidirectional DC-DC converter 22 and the AC regenerative converter 23 are monitored so that no failure occurs. The battery 20 is charged by converting an AC voltage input to the AC regenerative converter 23 via the isolation transformer 24 into a DC voltage, and inputting the DC voltage to the bidirectional DC-DC converter 22 to supply a charging current to the battery 20. Supply. As shown in FIG. 3, FIG. 7 and FIG. 9, when current flows to the power source in the process of charging and discharging, current flows from the bidirectional DC-DC converter 22 to the AC regenerative converter 23 side. The AC regenerative converter 23 converts this DC current into a three-phase AC and uses the insulation transformer 24 as regenerative power to the AC power supply side. Therefore, since charging and discharging of the battery 20 are performed by the common bidirectional DC-DC converter 22, space saving and cost reduction can be achieved.

It is explanatory drawing of Example 1 of this invention. It is operation | movement explanatory drawing of Example 1 of this invention. It is explanatory drawing of operation | movement of Example 1 of this invention. It is explanatory drawing of operation | movement of Example 1 of this invention. It is explanatory drawing of operation | movement of Example 1 of this invention. It is explanatory drawing of operation | movement of Example 1 of this invention. It is explanatory drawing of operation | movement of Example 1 of this invention. It is explanatory drawing of operation | movement of Example 1 of this invention. It is explanatory drawing of operation | movement of Example 1 of this invention. It is explanatory drawing of Example 2 of this invention. It is explanatory drawing of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery 2 Current detection part 3 Power supply 4 Control part Q1-Q4 1st-4th field effect transistor L1 Choke coil C1, C2 Capacitor

Claims (6)

In a bidirectional DC-DC converter for charging and discharging a battery,
A field effect transistor is connected in a full bridge, a power source is connected to one opposing terminal of the full bridge connection, the battery is connected to the other opposing terminal via a choke coil, and the field effect transistor is turned on and off. A bidirectional DC-DC converter comprising a control unit that controls and charges or discharges the battery. In a bidirectional DC-DC converter for charging and discharging a battery,
First and second field effect transistors are connected in series, third and fourth field effect transistors are connected in series, and a connection point between the first field effect transistor and the third field effect transistor; A connection point between the second field effect transistor and the fourth field effect transistor is connected to a power source, and a connection point between the first field effect transistor and the second field effect transistor is connected to the third field effect transistor. The battery is connected to a connection point between the field effect transistor and the fourth field effect transistor via a choke coil, and the on and off of the first to fourth field effect transistors are controlled to control the battery. A bidirectional DC-DC converter comprising a control unit that performs charging or discharging.   The control unit turns on the first and fourth field effect transistors and charges the battery from the power source through the choke coil, and then turns off the first and fourth field effect transistors to turn the first and fourth field effect transistors off. 3. The control system according to claim 2, wherein the battery charging current is stored in the choke coil via the parasitic diodes of the second and third field effect transistors. Bidirectional DC-DC converter.   The controller turns on the fourth field effect transistor after turning on the first and fourth field effect transistors and charging the battery from the power supply via the choke coil. 3. The bidirectional DC according to claim 2, wherein a control is performed to flow a charging current of the battery by energy stored in the choke coil via an effect transistor and a parasitic diode of the second field effect transistor. DC converter.   The control unit turns on the second and third field effect transistors and discharges the battery through the choke coil with a voltage obtained by adding the voltage of the power source to the voltage of the battery, and the second and second field effect transistors are discharged. 3 is turned off, and the battery as regenerative power is supplied to the power supply via the parasitic diodes of the first and fourth field effect transistors by the sum of the voltage of the energy stored in the choke coil and the voltage of the battery. The bidirectional DC-DC converter according to claim 2, wherein the bidirectional DC-DC converter has a configuration for performing a control for continuing the discharge of the current.   The control unit turns on the second field effect transistor and discharges the battery via the second field effect transistor and a parasitic diode of the fourth field effect transistor, so that the second field effect is obtained. The transistor is turned off, and the battery is continuously discharged as regenerative power through the parasitic diodes of the first and fourth field effect transistors by the sum of the voltage of the energy stored in the choke coil and the voltage of the battery. The bidirectional DC-DC converter according to claim 2, wherein the bidirectional DC-DC converter has a configuration for performing control.

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